The generality and mechanism of the verification reaction, or hydrolytic deacylation of misacylated tRNA, is under study. Similarly, attempts are being made to define those areas of common tRNA structure which account for their misacylation, or alternatively, which help distinguish them from other tRNA's of the same species. Some of the later studies focus on Su plus 7 tRNA, an amber suppressor which has also gained a new acylation specificity due to a single mutation of the anticodon. Finally, attempts are near success on a chemical method capable of determining the positions of features of tRNA primary structure relative to each other in space.